Pain can adversely affect patients in many different ways. It can keep the patient from being active, sleeping well, enjoying family and friends, and from eating. Pain can make the patient feel afraid or depressed and prevent full participation in general rehabilitation programs and may even slow recovery.
Proper pain control is of prime importance to anyone treating many different diseases or conditions. Proper pain relief imparts significant physiological and psychological benefits to the patient. Not only does effective pain relief mean a smoother more pleasant recovery (e.g., mood, sleep, quality of life, etc.) with earlier discharge from medical/surgical/outpatient facilities, but it may also reduce the onset of chronic pain syndromes (e.g., fibromyalgia, myalgia, etc.).
Pain serves the important biological function of signaling the presence of damage or disease within the body and is often accompanied by inflammation (redness, swelling, and/or burning). There are two categories of pain: acute pain and neuropathic pain. Acute pain refers to pain experienced when tissue is being damaged or is damaged. Acute pain serves at least two physiologically advantageous purposes. First, it warns of dangerous environmental stimuli (such as hot or sharp objects) by triggering reflexive responses that end contact with the dangerous stimuli. Second, if reflexive responses do not avoid dangerous environmental stimuli effectively, or tissue injury or infection otherwise results, acute pain facilitates recuperative behaviors. For example, acute pain associated with an injury or infection encourages an organism to protect the compromised area from further insult or use while the injury or infection heals. Once the dangerous environmental stimulus is removed, or the injury or infection has resolved, acute pain, having served its physiological purpose, ends. As contrasted to acute pain, in general, neuropathic pain serves no beneficial purpose. Neuropathic pain results when pain associated with an injury or infection continues in an area once the injury or infection has resolved.
There are many painful disease or conditions that require proper pain and/or inflammation control, including but not limited to rheumatoid arthritis, osteoarthritis, a spinal disc herniation (i.e., sciatica), carpal/tarsal tunnel syndrome, lower back pain, lower extremity pain, upper extremity pain, cancer, tissue pain and pain associated with injury or repair of cervical, thoracic, and/or lumbar vertebrae or intervertebral discs, rotator cuff, articular joint, TMJ, tendons, ligaments, muscles, spondilothesis, stenosis, discogenic back pain, and joint pain or the like.
One particularly painful disease is sciatica. Sciatica is a chronic disease that often can be very debilitating and may take a terrible toll on those with the disease as well as their families, friends and caregivers. Sciatica is a very painful disease associated with the sciatic nerve which runs from the lower part of the spinal cord (the lumbar region), down the back of the leg and to the foot. Sciatica generally begins with a herniated disc, which later leads to local immune system activation. The herniated disc also may damage the nerve root by pinching or compressing it, leading to additional immune system activation in the area. There has been considerable interest in developing effective treatments for this painful disease, yet to date current treatments of sciatica are only partially effective.
Another particularly painful disease is spinal stenosis, where there is progressive constriction of the spinal canal and as it narrows, the nerve elements that reside within it become progressively more crowded. Eventually, the canal dimensions become sufficiently small-so as to significantly compress the nerve elements and produce pain, weakness, sensory changes, clumsiness and other manifestation of nervous system dysfunction. The disease causes lower back pain, lower extremity pain, lower extremity weakness, limitation of mobility and the high disability rates that often afflict the elderly.
Spondylolisthesis is another painful disease. Spondylolisthesis is a displacement disorder of the lumbar or cervical spine, in which one vertebral body is forwardly displaced over another vertebral body. Spondylolisthesis may be caused by a traumatic event or by degeneration of the spine. At times, the displacement disorder is accompanied by or caused by a fracture or partial collapse of one or more vertebrae or degeneration of a disc in the spine. Patients who suffer from such conditions can experience moderate to severe distortion of the thoracic skeletal structure, diminished ability to bear loads, loss of mobility, extreme and debilitating pain, and oftentimes suffer neurological deficits in nerve function
One known class of pharmaceuticals to treat pain is opiods. This class of compounds is well-recognized as being among the most effective type of drugs for controlling pain. Unfortunately, because opiods are administered systemically, the associated side effects raise significant concerns, including disabling the patient, depressing the respiratory system, constipation, and psychoactive effects such as sedation and euphoria, thereby instituting a hurdle to recovery and regained mobility. Further, because of these side-effects, physicians typically limit the administration of opiods to within the first 24 hours post-surgery. Thus, there has been a considerable interest in using non-narcotic drugs that deliver direct, localized pain control at a target tissue site.
One pharmaceutical that is known to the medical profession is sulindac, (commercially available as Clinoril® from Sigma as a free acid) which is widely recognized as a non-steroidal anti-inflammatory of the arylalkanoic acid class. It may be represented by the following chemical formula C20H17FO3S. Sulindac is a prodrug, derived from sulfinylindene that is converted in the body to an active NSAID (non-steroidal anti-inflammatory agent). More specifically, the agent is converted by liver enzymes to a sulfide that is excreted in the bile and then reabsorbed from the intestine. This is thought to help maintain constant blood levels with reduced gastrointestinal side effects.
However, to date sulindac has not been appreciated as an effective treatment for pain and/or inflammation in sustained release formulations that provide relief over at least 3 days. Thus, there is a need to develop effective formulations of this compound for this application.